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Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 98 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0300, DTC P0301, DTC P0302, DTC P0303, DTC P0304, DTC P0305, DTC P0306, DTC P0307 Or DTC P0308 >> Diagnosis & Repair

Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.
  1. If any other codes (besides DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308) are being output, diagnose relevant DTC. If not, go to next step.
  2. Check vacuum hoses for leaks, blockage and proper routing. Also, check wiring and connectors for damage or poor connections. If problem exists, repair as necessary and perform CONFIRMATION DRIVING PATTERN . If problem does not exist, go to next step.
  3. Check connection of PCV piping. Repair as necessary. If okay, go to next step.
  4. Connect the hand-held tester to the DLC3. Turn the ignition switch ON and push the hand-held tester main switch ON. Start engine. Read misfire on hand-held tester. If misfire is on 1-2 cylinders, go to next step. If misfire is on more than 3 cylinders, go to step  14.
  5. Check spark and ignition system. See Fig 1. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If problem exists, repair as necessary. If problem does not exist, go to next step.
    Fig 1: Checking Spark Plug
    G00165128Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  6. Disconnect the spark plug. Change the normal spark plug. Install the normal spark plug to the ignition coil with igniter. Disconnect the injector connector. Ground the spark plug. Check if spark occurs while the engine is being cranked. To prevent excess fuel from being injected, don't crank engine for more than 5-10 seconds at a time. If spark jumps across electrode gap, replace spark plug. If not, go to next step.
  7. Check for open and short in harness and connector between ignition coil and ECM. If okay, replace ignition coil with igniter, then confirm tat there is no misfire. If not okay, go to next step.
  8. Remove the engine room ECU cover. Turn the ignition switch ON. Measure the voltage between applicable terminal of the ECM connectors and body ground. See Fig 2. If okay, voltage should be 9-14 volts. If using oscilloscope, with the engine idling, check the waveform between terminals No. 1-8 and E01 of the ECM connectors. The correct waveform is as shown. See Fig 3. If okay, go to step  11. If not okay, go to next step.
    Fig 2: Checking Circuit Between ECM & Ground
    G00165129Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    Fig 3: Identifying Injector Signal Waveform
    G00165130Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  9. Check spark plug and spark of misfiring cylinder. Replace injector as necessary. If okay, go to next step.
  10. Check for open and short in harness and connector between TG2 and injector, injector and ECM of misfiring cylinder. Repair as necessary. If okay, go to next step.
  11. Check injector injection of misfiring cylinder. Replace injector as necessary. If okay, go to next step.
  12. Check compression pressure of misfiring cylinder. Repair as necessary. If okay, go to next step.
  13. Check valve clearance of misfiring cylinder. Repair as necessary. If okay, go to next step.
  14. If misfire was in 1-2 cylinders, go to next step. If misfire was in more than 3 cylinders, check for intermittent problems.
  15. Check valve timing. Adjust as necessary. If okay, go to next step.
  16. Check fuel pressure. Repair fuel pump, pressure regulator, fuel pipe line and filter as necessary. If okay, go to next step.
  17. Check mass airflow sensor and engine coolant temperature sensor. Repair or replace as necessary. If okay, go to next step.
  18. Check for intermittent problems.
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